1. Field of the Invention
The invention relates to amplifier divider/combiners for dividing input rf energy between a plurality of amplifying channels and then combining the outputs to achieve high power out.
2. Description of the Prior Art
Solid state microwave amplifying devices are limited in power. To overcome this, it is a common practice to divide an input signal among a plurality of amplifiers and then combine the outputs. In the beginning, the amplifiers delivered only fractional watts, so that on combination the output might provide several watts.
Divider/combiners using distributed amplifier components in impedance networks became quite common as described in U.S. Pat. No. 4,769,618. It has been found that the amplifying devices themselves in these networks had to be extremely well matched. This is not only costly, but replacement in the field becomes virtually impossible.
U.S. Pat. No. 4,263,559 of Pang T. Ho uses directional couplers of the interdigital variety in microstrip for his power divider/combiners. These apparently have no phasing problems and probably work well at low power levels. Unlike impedance combiner networks, directional couplers are quite tractable to mismatch in the amplifiers.
Unfortunately, when high power levels are required, microstrip couplers are not adequate and the available couplers for the higher power levels produce a new series of problems. Many are difficult to package in any compact manner. Most have limitations on the range of coupling level (tightness or loosenes) available and phase through the couplers often is a function of coupling level.